Power Amplifier Linearization Feedback Methods and Systems

• US 20110190028A1
• Filed: 01/26/2011
• Published: 08/04/2011
• Est. Priority Date: 02/01/2010
• Status: Active Grant

• Current Assignee: Intersil Americas LLC (Renesas Electronics Corporation)
• Original Assignee: Intersil Americas LLC (Renesas Electronics Corporation)
• Inventors: Chen, Wei, Hahn, Wilhelm Steffen
• Granted Patent: US 8,615,207 B2
• Time in Patent Office: Days
• US Class Current: 455/550.1
• CPC Class Codes: H03F 1/34 Negative-feedback-circuit arrangements with or without positive feedback H03F1/02 - H03F1/30, H03F1/38 - H03F1/50, H03F3/50 take precedence ; for rejection of common mode signals H03F3/45479
• CPC Class Codes: H03F 1/345 using hybrid or directional couplers
• CPC Class Codes: H03F 3/24 of transmitter output stages
• CPC Class Codes: H04B 2001/0433 with linearisation using feedback

Abstract

Linearizers can improve the linearity of power amplifiers by canceling or reducing amplitude of non-linearity components, (e.g., IM3, IM5, IM7, IM9, etc.) generated by the power amplifier. The linearizers can obtain samples of signals output by the power amplifier and process the samples to produce a compensation signal that is applied onto or into a transmission path leading to the power amplifier'"'"'s input. The compensation signal is generated such that when amplified by the power amplifier, the amplified compensation signal cancels or reduces at least a portion of the non-linearity components produced by the power amplifier. A controller can improve the correction of the non-linearity components by executing one or more calibration algorithms and/or one or more tuning algorithms and adjusting settings of the linearizer based on the results of the algorithm(s).

Claims

1. A system for improving linearity of a power amplifier, comprising:

a first input operable to couple to an input signal path of the power amplifier for obtaining a first sample of an input signal of the power amplifier;

a second input operable to couple to an output signal path of the power amplifier for obtaining a second sample of an output signal of the power amplifier, the output signal comprising at least one non-linearity component imposed on the output signal by the power amplifier, the second sample comprising at least one sampled non-linearity component corresponding to the at least one non-linearity component;

an output operable to couple to the input signal path of the power amplifier, the output for applying a linearity improving signal to the input signal path; and

a linearizer electrically coupled to the first input, the second input, and the output, the linearizer comprising;

a first signal canceller for receiving the first sample from the first input and the second sample from the second input and deducting the first sample from the second sample to produce an intermediate signal comprising the at least one sampled non-linearity component; and

a second signal canceller coupled between the first signal canceller and the output, the second signal canceller operable to produce the linearity improving signal by adjusting at least one of amplitude, phase, and delay of the at least one sampled non-linearity component of the intermediate signal, the linearity improving signal operable to reduce an intensity of the at least one non-linearity component in response to being coupled to the input signal path and amplified by the power amplifier.

2. The system of claim 1, wherein the first input, the second input, and the output each comprise a coupler.

3. The system of claim 1, further comprising a first attenuator disposed between the first input and the first signal canceller and a second attenuator disposed between the second input and the first signal canceller.

4. The system of claim 1, further comprising an amplifier disposed between the output of the second signal canceller and the output.

5. The system of claim 1, wherein the first sample comprises a modulated signal component and the second sample comprises an amplitude adjusted modulated signal component, and wherein the first canceller reduces intensity of the amplitude adjusted modulated signal component while leaving intensity of the at least one sampled non-linearity component of the second sample substantially unchanged to produce the intermediate signal.

6. The system of claim 1, further comprising:

a power detector for measuring intensity of the modulated signal component of the first sample; and

a controller for receiving the intensity measurement from the power detector and for adjusting at least one setting of the first signal canceller based on the intensity measurement.

7. The system of claim 1, wherein the first canceller is operable to adjust at least one of amplitude, phase, and delay of at least one component of the first sample based on an in-phase setting and a quadrature setting prior to deducting the first sample from the second sample.

8. The system of claim 1, wherein the second signal canceller adjusts at least one of amplitude, phase, and delay of the at least one sampled non-linearity component of the intermediate signal based on an in-phase setting and a quadrature setting.

9. The system of claim 1, further comprising:

a power detector for measuring intensity of the at least one sampled non-linearity component; and

a controller for receiving the intensity measurement from the power detector and for adjusting at least one setting of the second signal canceller based on the intensity measurement.

10. The system of claim 1, further comprising:

a power detector comprising a power detector input and a power detector output;

a switch comprising;

a first switch input coupled to an input of the first signal canceller;

a second switch input coupled to the output of the first signal canceller;

a switch output coupled to the power detector input; and

a controller electrically coupled to the switch and operable to configure the switch to couple the first switch input to the switch output or the second switch input to the switch output.

11. The system of claim 10, wherein the power detector comprises:

a peak detector for measuring an intensity of a signal; and

a filter disposed between the power detector input and the peak detector.

12. The system of claim 1, further comprising a frequency converting mixer disposed between the first input and the first signal canceller.

13. The system of claim 1, wherein the linearizer is fabricated in one or more integrated circuits.

14. A method for reducing non-linearity components imposed on a signal output by a power amplifier, the method comprising:

receiving a second sample of an output signal output by the power amplifier, the output signal comprising at least one non-linearity component imposed on the output signal by the power amplifier, the first sample comprising at least one sampled non-linearity component corresponding to the at least one non-linearity component;

determining an intensity level of the at least one sampled non-linearity component;

generating a compensation signal by adjusting at least one of phase, amplitude, and delay of the at least one sampled non-linearity component based on the intensity level;

applying the compensation signal to an input of the power amplifier; and

in response to applying the compensation signal to the input, reducing amplitude of the at least one non-linearity component.

15. The method of claim 14, wherein the at least one non-linearity component comprises an intermodulation product imposed on the output signal by the power amplifier.

16. The method of claim 14, further comprising:

receiving a first sample of an input signal to the power amplifier; and

reducing an intensity level of a fundamental tone component of the second sample by subtracting the first sample from the second sample.

17. The method of claim 14, wherein the at least one of phase, amplitude, and delay is adjusted based on an in-phase setting and a quadrature setting.

18. The method of claim 17, further comprising executing a computer program using the intensity level as a feedback value to determine the in-phase setting and the quadrature setting.

19. A method for reducing non-linearity components of an output signal of a power amplifier, the method comprising:

(a) obtaining a first sample of an input signal from an input signal path to the power amplifier, the first sample comprising a first modulated signal component;

(b) obtaining a second sample of an output signal of the power amplifier, the output signal comprising at least one non-linearity component imposed on the output signal by the power amplifier, the second sample comprising a second modulated signal component and at least one sampled non-linearity component;

(c) generating an intermediate signal by reducing amplitude of the second modulated signal component of the second sample by deducting the first sample from the second sample;

(d) determining an intensity level of the at least one sampled non-linearity component;

(e) producing a compensation signal by adjusting at least one of phase, amplitude, and delay of the at least one sampled non-linearity component based on the intensity level;

(f) applying the compensation signal to the input signal path; and

(g) in response to applying the compensation signal to the input signal path and to the power amplifier amplifying the compensation signal, reducing an intensity level of the at least one non-linearity component.

20. The method of claim 19, further comprising repeating (a) through (g) for a plurality of iterations to improve the reduction of the intensity level of the at least one non-linearity component.

21. The method of claim 19, further comprising converting a frequency of the second sample.

22. The method of claim 19, further comprising converting both the frequency of the input signal and the frequency of the output signal to a similar frequency.

23. The method of claim 19, wherein the compensation signal is applied to the input signal path between a location where the first sample is obtained and an input of the power amplifier.

24. The method of claim 19, wherein the at least one of phase, amplitude, and delay is adjusted based on an in-phase setting and a quadrature setting.

25. The method of claim 19, further comprising executing a computer program using the intensity level as a feedback value to determine the in-phase setting and the quadrature setting.

26. A cellular telephone system comprising:

a first input configured to receive a first sample of an amplifier input;

a second input configured to receive a second sample of the amplifier output that comprises a non-linearity;

an output configured to feed an output signal towards the amplifier input;

a linearization circuit electrically coupled to the first input, the second input, and the output, the linearization circuit comprising;

a first signal canceller, connected to the first input and the second input, operable to generate a first signal based on a difference between the second sample and the first sample; and

a second signal canceller electrically connected to the first signal canceller, operable to produce the output signal in response to adjusting at least one of amplitude, phase, and delay of the first signal.

27. The cellular telephone system of claim 26, wherein the output signal is operable to reduce the non-linearity in response to being amplified by the amplifier.

28. A method, comprising:

receiving a first sample of an amplifier input;

receiving a second sample of the amplifier output that comprises a non-linearity;

generating a first signal based on a difference between the second sample and the first sample; and

producing an output signal, operable to improve the non-linearity, in response to adjusting at least one of amplitude, phase, and delay of the first signal.